Ali Akbar Tajari Siahmarzkooh - PhD student in Computer Sciences at University of Tabriz
Jaber Karimpour - Assistant Professor, Department of Computer Sciences at University of Tabriz

Authentication is a mechanism by which any entity can check whether its partner is one who claims to be in a relationship or is a disrupting that has been replaced by real party. One of the authentication protocols is Kerberos where timestamp is used to avoid sending repeated and unfeigned messages by Trudy. In this article a counter variable is considered for each client that represents number of sent messages from the client to servers. Advantage of this variable that host at ticket granting server is aware of repeated message during send it. Also, at servers we used a binary tree structure to store the messages and searching between them. Simulation results show significant improvement in the face of replay attacks by Trudy and response time to service at Kerberos Cryptographic Network.

Authentication, Kerberos Protocol, Replay Attack, Ticket Granting Server, Binary Tree